04 MYTILIDJS. 



duck's stomach, shot in Northumberland, sub fide Kingii, is 

 considered by him of doubtful British origin. We have the 

 specimen. 



PINNA, Linnaeus. 

 P. PECTINATA, Ibid. 



P. pectinata, Brit. Moll. ii. p. 255, pi. 43. f. 1, 2, and pi. 53. f. 8. 

 P. ingens and P. papyracea, Auct. 



Animal elongated, body large ; mantle open, of delicate tex- 

 ture except at the margin, which is furnished at the posterior 

 end with two rows of tentacular cirrhi, but only one at its 

 anterior portion. There are on each side a pair of large 

 branchiae of nearly equal size and crescent-shaped, united by 

 two wide labia, foliaceous on the internal surface, which fall 

 on each side the body, connected with the buccal orifice and 

 a pair of short, narrow, lanceolate palpi, which appear dispro- 

 portionate for so large an animal. The mantle forms neither 

 siphons nor even sessile orifices. The foot is conically sub- 

 cylindrical, not long, with a byssal groove at the posterior bend, 

 from which a large fine silky byssus of attachment issues ; 

 this the animal has the power to discard when it wishes to 

 change place, and can refix itself by spinning in a very short 

 time a new one. 



Having only seen very young examples alive, we have for 

 descriptive assistance had recourse to M. Poli, ' Test. Sicil.' 



AVICULA, Lamarck. 



A. TARENTINA, Ibid. 



A. tarentina, Brit. Moll. ii. p. 251 , pi. 42. f. 1, 2, 3, and (animal) pi. S. 

 f. 4. 



Animal suboval compressed; mantle entirely open, having 

 the margin fringed, as in Pinna, with tentacular filaments ; 

 there are no siphons nor orifices. The dorsal range of the 

 shell usually forms a slender linear posterior elongation, which 

 is lined by a fold of the mantle. On each side of the body there 

 are a pair of nearly similar-formed branchiae of crescent shape, 



